CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL - USD ($) shares in Thousands, $ in Thousands	Total	Common Unitholders [Member]	Accumulated Other Comprehensive (Loss) [Member]
Balance at Sep. 30, 2017	$ 552,982	$ 581,794	$ (28,812)
Balance (in units) at Sep. 30, 2017		61,105
Net income	76,534	$ 76,534
Amortization of net actuarial losses and prior service credits into earnings and net change in funded status of benefit plans	4,142		4,142
Partnership distributions	(147,185)	(147,185)
Common Units issued under Restricted Unit Plans	(847)	$ (847)
Common Units issued under Restricted Unit Plans (in units)		300
Recognition in earnings of net actuarial loss for pension settlement	0
Compensation costs recognized under Restricted Unit Plans	8,198	$ 8,198
Balance at Sep. 29, 2018	493,824	$ 518,494	(24,670)
Balance (in units) at Sep. 29, 2018		61,405
Net income	68,632	$ 68,632
Amortization of net actuarial losses and prior service credits into earnings and net change in funded status of benefit plans	(1,516)		(1,516)
Partnership distributions	(147,882)	(147,882)
Common Units issued under Restricted Unit Plans	(1,349)	$ (1,349)
Common Units issued under Restricted Unit Plans (in units)		261
Recognition in earnings of net actuarial loss for pension settlement	0
Common Units issued for acquisition of business	1,600	$ 1,600
Common Units issued for acquisition of business (in units)		69
Compensation costs recognized under Restricted Unit Plans	10,521	$ 10,521
Balance at Sep. 28, 2019	423,830	$ 450,016	(26,186)
Balance (in units) at Sep. 28, 2019		61,735
Cumulative adjustment for lease accounting standard	108	$ 108
Net income	60,758	60,758
Amortization of net actuarial losses and prior service credits into earnings and net change in funded status of benefit plans	(641)		(641)
Partnership distributions	(130,206)	(130,206)
Common Units issued under Restricted Unit Plans	(1,761)	$ (1,761)
Common Units issued under Restricted Unit Plans (in units)		411
Recognition in earnings of net actuarial loss for pension settlement	1,051		1,051
Compensation costs recognized under Restricted Unit Plans	9,242	$ 9,242
Balance at Sep. 26, 2020	$ 362,381	$ 388,157	$ (25,776)
Balance (in units) at Sep. 26, 2020		62,146